The position of the Keruvim reflect the relationship between Hashem and Bnei Yisroel. When we are doing the mitzvos they face each other. When we stray the Keruvim stand back to back. The gemara in Yuma 54b says that when the enemy came into the Kodesh Kodashim they found the two Keruvim embracing like a husband and wife. At this low point in our relationship with Hashem as the Bais HaMikdash is going up in flames how can this be?
The Bnei Yissaschar answers that even the happiest couples do not constantly show emotion when they are together. If you want to see how much a couple loves each other you need to witness them when they are departing from each other. Although Hashem was departing from us with the destruction of the Bais HaMikdash we are still his beloved nation. Our departure to our bitter galus let loose torrents of pent up emotion between Hashem and us. This was the embrace that the enemy witnessed.
